This invention relates generally to renal function in a living subject, and more particularly the invention relates to measuring renal extraction fraction using computed tomography (CT).
Renal extraction fraction (EF) is an important physiologic measurement of the function of the kidneys in a living subject. Clearance techniques are classically used to measure renal physiologic parameters such as EF, and the direct measurement of clearance can be made through the collection of multiple urine and blood samples for determining the filtration of markers by the kidneys. However, these conventional clearance techniques have many disadvantages and require timed urine collection.
Katzberg et al., U.S. Pat. No. 6,122,540 proposes a method for measurement of renal filtration through use of magnetic resonance imaging. The measurement of renal plasma flow and filtration fraction includes measuring longitudinal spin relaxation time (T1) of blood with a contrast agent and with blood with an injected longitudinal spin relaxation time contrast agent. More specifically, T1 of blood flow into the kidney and T1 of post filtered blood flow out of the kidney are measured.
The present invention is directed to measuring renal extraction fraction through use of contrast enhanced CT using x-ray transmission measurements of blood with and without contrast agents.